Electronic Devices With Folding Displays Having Flexible Area Support Structures

ABSTRACT

A foldable display may have a display cover layer and display panel that bend around a bend axis. The display panel may have an array of pixels configured to display an image through the display cover layer. The display cover layer may be formed from a layer of glass. A recess may be formed in the layer of glass that extends along and overlaps the bend axis. The recess forms a flexible locally thinned portion in the glass that allows the display cover layer to bend. Polymer may be formed in the recess. Stiffening structures such as glass strips and glass beads of one or more diameters may be embedded in the polymer to help resist inward compression of the surface of the display cover layer in the locally thinned region while allowing the display cover layer to bend about the bend axis.

This application claims the benefit of provisional patent applicationNo. 63/127,690, filed Dec. 18, 2020, and provisional patent applicationNo. 63/166,555, filed Mar. 26, 2021, which are hereby incorporated byreference herein in their entireties.

FIELD

This relates generally to electronic devices, and, more particularly, toelectronic devices with displays.

BACKGROUND

Electronic devices often have displays. Portability may be a concern forsome devices, which tends to limit available real estate for displays.

SUMMARY

An electronic device may be provided with a foldable housing that allowsthe device to fold and unfold about a bend axis. A flexible display maybe mounted in the foldable housing. The flexible display may have anarray of pixels forming a display panel. The display panel may beconfigured to bend along the bend axis as the device is folded.

The flexible display may have a display cover layer that overlaps thedisplay panel. The display cover layer may be formed from a layer ofglass. A groove-shaped recess may be formed in the layer of glass thatruns parallel to the bend axis. The recess forms a flexible locallythinned portion in the glass over the bend axis that allows the displayto bend about the bend axis.

Polymer may be placed in the recess to help planarize the inner surfaceof the display cover layer. Stiffening structures such as glass stripsand/or glass beads of one or more diameters may be embedded in thepolymer to help stiffen the surface of the display cover layer in thelocally thinned region so that the outer surface of the display coverlayer is not too easily deformed by external pressure from an objectsuch as a stylus. While supporting the outer surface of the displaycover layer, the stiffening structures allow the display cover layer tobend satisfactorily about the bend axis.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of an illustrative electronic device inaccordance with an embodiment.

FIG. 2 is a perspective view of an illustrative electronic device with adisplay in accordance with an embodiment.

FIG. 3 is a cross-sectional side view of an illustrative electronicdevice in accordance with an embodiment.

FIG. 4 is a cross-sectional side view of an illustrative display havinga cover layer with a locally thinned hinge region in accordance with anembodiment.

FIG. 5 is a cross-sectional side view of an illustrative locally thinneddisplay cover layer having outer and inner coatings in accordance withan embodiment.

FIG. 6 is a cross-sectional side view of an illustrative locally thinneddisplay cover layer with an inner coating that is formed as an integralportion of a recess-filling layer in accordance with an embodiment.

FIG. 7 is a cross-sectional side view of an illustrative locally thinneddisplay cover layer with a polymer filler having embedded particles inaccordance with an embodiment.

FIG. 8 is a graph in which mean particle diameter in an illustrativerecess-filling polymer layer has been plotted as a function of distancethrough the layer in accordance with an embodiment.

FIG. 9 is a cross-sectional side view of an illustrative display coverlayer with a locally thinned portion in accordance with an embodiment.

FIGS. 10 and 11 are cross-sectional side views of illustrative displaycover layers with locally thinned areas having polymer with embeddedstiffening members in accordance with embodiments.

FIG. 12 is a cross-sectional side view of an illustrative stiffeningmember for adding compression rigidity to a locally thinned portion of acover layer in accordance with an embodiment.

DETAILED DESCRIPTION

Electronic devices may be provided with displays. Displays may be usedfor displaying images for users. Displays may be formed from arrays oflight-emitting diode pixels or other pixels. For example, a device mayhave an organic light-emitting diode display or a display formed from anarray of micro-light-emitting diodes (e.g., diodes formed fromcrystalline semiconductor dies).

A schematic diagram of an illustrative electronic device having adisplay is shown in FIG. 1. Device 10 may be a cellular telephone,tablet computer, laptop computer, wristwatch device or other wearabledevice, a television, a stand-alone computer display or other monitor, acomputer display with an embedded computer (e.g., a desktop computer), asystem embedded in a vehicle, kiosk, or other embedded electronicdevice, a media player, or other electronic equipment. Configurations inwhich device 10 is a cellular telephone, tablet computer, or otherportable electronic device may sometimes be described herein as anexample. This is illustrative. Device 10 may, in general, be anysuitable electronic device with a display.

Device 10 may include control circuitry 20. Control circuitry 20 mayinclude storage and processing circuitry for supporting the operation ofdevice 10. The storage and processing circuitry may include storage suchas nonvolatile memory (e.g., flash memory or otherelectrically-programmable-read-only memory configured to form a solidstate drive), volatile memory (e.g., static or dynamicrandom-access-memory), etc. Processing circuitry in control circuitry 20may be used to gather input from sensors and other input devices and maybe used to control output devices. The processing circuitry may be basedon one or more microprocessors, microcontrollers, digital signalprocessors, baseband processors and other wireless communicationscircuits, power management units, audio chips, application specificintegrated circuits, etc. During operation, control circuitry 20 may usea display and other output devices in providing a user with visualoutput and other output.

To support communications between device 10 and external equipment,control circuitry 20 may communicate using communications circuitry 22.Circuitry 22 may include antennas, radio-frequency transceiver circuitry(wireless transceiver circuitry), and other wireless communicationscircuitry and/or wired communications circuitry. Circuitry 22, which maysometimes be referred to as control circuitry and/or control andcommunications circuitry, may support bidirectional wirelesscommunications between device 10 and external equipment over a wirelesslink (e.g., circuitry 22 may include radio-frequency transceivercircuitry such as wireless local area network transceiver circuitryconfigured to support communications over a wireless local area networklink, near-field communications transceiver circuitry configured tosupport communications over a near-field communications link, cellulartelephone transceiver circuitry configured to support communicationsover a cellular telephone link, or transceiver circuitry configured tosupport communications over any other suitable wired or wirelesscommunications link). Wireless communications may, for example, besupported over a Bluetooth® link, a WiFi® link, a wireless linkoperating at a frequency between 6 GHz and 300 GHz, a 60 GHz link, orother millimeter wave link, cellular telephone link, wireless local areanetwork link, personal area network communications link, or otherwireless communications link. Device 10 may, if desired, include powercircuits for transmitting and/or receiving wired and/or wireless powerand may include batteries or other energy storage devices. For example,device 10 may include a coil and rectifier to receive wireless powerthat is provided to circuitry in device 10.

Device 10 may include input-output devices such as devices 24.Input-output devices 24 may be used in gathering user input, ingathering information on the environment surrounding the user, and/or inproviding a user with output. Devices 24 may include one or moredisplays such as display 14. Display 14 may be an organic light-emittingdiode display, a liquid crystal display, an electrophoretic display, anelectrowetting display, a plasma display, a microelectromechanicalsystems display, a display having a pixel array formed from crystallinesemiconductor light-emitting diode dies (sometimes referred to asmicroLEDs), and/or other display. Configurations in which display 14 isan organic light-emitting diode display or microLED display aresometimes described herein as an example.

Display 14 may have an array of pixels configured to display images fora user. The pixels may be formed as part of a display panel that isbendable. This allows device 10 to be folded and unfolded about a bendaxis. For example, a flexible (bendable) display in device 10 may befolded so that device 10 may be placed in a compact shape for storageand may be unfolded when it is desired to view images on the display.

Sensors 16 in input-output devices 24 may include force sensors (e.g.,strain gauges, capacitive force sensors, resistive force sensors, etc.),audio sensors such as microphones, touch and/or proximity sensors suchas capacitive sensors (e.g., a two-dimensional capacitive touch sensorintegrated into display 14, a two-dimensional capacitive touch sensoroverlapping display 14, and/or a touch sensor that forms a button,trackpad, or other input device not associated with a display), andother sensors. If desired, sensors 16 may include optical sensors suchas optical sensors that emit and detect light, ultrasonic sensors,optical touch sensors, optical proximity sensors, and/or other touchsensors and/or proximity sensors, monochromatic and color ambient lightsensors, image sensors, fingerprint sensors, temperature sensors,sensors for measuring three-dimensional non-contact gestures (“airgestures”), pressure sensors, sensors for detecting position,orientation, and/or motion (e.g., accelerometers, magnetic sensors suchas compass sensors, gyroscopes, and/or inertial measurement units thatcontain some or all of these sensors), health sensors, radio-frequencysensors, depth sensors (e.g., structured light sensors and/or depthsensors based on stereo imaging devices that capture three-dimensionalimages), optical sensors such as self-mixing sensors and light detectionand ranging (lidar) sensors that gather time-of-flight measurements,humidity sensors, moisture sensors, gaze tracking sensors, and/or othersensors. In some arrangements, device 10 may use sensors 16 and/or otherinput-output devices to gather user input. For example, buttons may beused to gather button press input, touch sensors overlapping displayscan be used for gathering user touch screen input, touch pads may beused in gathering touch input, microphones may be used for gatheringaudio input, accelerometers may be used in monitoring when a fingercontacts an input surface and may therefore be used to gather fingerpress input, etc.

If desired, electronic device 10 may include additional components (see,e.g., other devices 18 in input-output devices 24). The additionalcomponents may include haptic output devices, audio output devices suchas speakers, light-emitting diodes for status indicators, light sourcessuch as light-emitting diodes that illuminate portions of a housingand/or display structure, other optical output devices, and/or othercircuitry for gathering input and/or providing output. Device 10 mayalso include a battery or other energy storage device, connector portsfor supporting wired communication with ancillary equipment and forreceiving wired power, and other circuitry.

FIG. 2 is a perspective view of electronic device 10 in an illustrativeconfiguration in which device 10 is a portable electronic device such asa cellular telephone or tablet computer. As shown in FIG. 2, device 10may have a display such as display 14. Display 14 may cover some or allof the front face of device 10. Touch sensor circuitry such astwo-dimensional capacitive touch sensor circuitry may be incorporatedinto display 14.

Display 14 may be mounted in housing 12. Housing 12 may form front andrear housing walls, sidewall structures, and/or internal supportingstructures (e.g., a frame, an optional midplate member, etc.) for device10. Glass structures, transparent polymer structures, and/or othertransparent structures that cover display 14 and other portions ofdevice 10 may provide structural support for device 10 and may sometimesbe referred to as housing structures. For example, a transparent housingportion such as a glass or polymer housing structure that covers andprotects a pixel array in display 14 may serve as a display cover layerfor the pixel array while also serving as a housing wall on the frontface of device 10. In configurations in which a display cover layer isformed from glass, the display cover layer may sometime be referred toas a display cover glass or display cover glass layer. The portions ofhousing 12 on the sidewalls and rear wall of device 10 may be formedfrom glass or other transparent structures and/or opaque structures.Sidewalls and rear wall structures may be formed as extensions to thefront portion of housing 12 (e.g., as integral portions of the displaycover layer) and/or may include separate housing wall structures.

Housing 12 may have flexible structures (e.g., bendable housing wallstructures) and/or hinge structures such as hinge 30. Hinge 30 may havea hinge axis aligned with device bend axis 28. Hinge 30 and/or flexiblehousing structures that overlap bend axis 28 may allow housing 12 tobend about bend axis 28. For example, housing 12 may have a firstportion on one side of bend axis 28 and a second portion on an opposingside of bend axis 28 and these two housing portions may be coupled byhinge 30 for rotational motion about axis 28.

As housing 12 is bent about bend axis 28, the flexibility of display 14allows display 14 to bend about axis 28. In an illustrativeconfiguration, housing 12 and display 14 may bend by 180°. This allowsdisplay 14 to be folded back on itself (with first and secondoutwardly-facing portions of display 14 facing each other). The abilityto place device 10 in a folded configuration in this way may help makedevice 10 compact so that device 10 can be stored efficiently. When itis desired to view images on display 14, device 10 may be unfolded aboutaxis 28 to place device 10 in the unfolded configuration of FIG. 2. Thisallows display 14 to lie flat and allows a user to view flat images ondisplay 14. The ability to fold display 14 onto itself allows device 10to exhibit an inwardly folding behavior. Display 14 may be sufficientlyflexible to allow device 10 to be folded outwardly and/or inwardly.

Device 10 of FIG. 2 has a rectangular outline (rectangular periphery)with four corners. As shown in FIG. 2, a first pair of parallel edges(e.g., the left and right edges of device 10 in the example of FIG. 2)may be longer than a second pair of parallel edges (e.g., the upper andlower edges of device 10 of FIG. 2) that are oriented at right angles tothe first pair of parallel edges. In this type of configuration, housing12 is elongated along a longitudinal axis that is perpendicular to bendaxis 28. Housing 12 may have other shapes, if desired (e.g., shapes inwhich housing 12 has a longitudinal axis that extends parallel to bendaxis 28). With an arrangement of the type shown in FIG. 2, the length ofdevice 10 along its longitudinal axis may be reduced by folding device10 about axis 28.

FIG. 3 is a cross-sectional side view of an illustrative foldableelectronic device. Device 10 of FIG. 3 may bend about bend axis 28. Bendaxis 28 may be aligned with display cover layer 14CG or other structuresin device 10. For example, bend axis 28 may pass through a portion ofdisplay cover layer 14CG or may be located above or below layer 14CG.

As shown in FIG. 3, display 14 includes an array of pixels P formingdisplay panel 14P under an inwardly facing surface of display coverlayer 14CG. Display panel 14P may be, for example, a flexible organiclight-emitting diode display or a microLED display in whichlight-emitting pixels are formed on a flexible substrate layer (e.g., aflexible layer of polyimide or a sheet of other flexible polymer).Flexible support layer(s) for display 14 may also be formed fromflexible glass, flexible metal, and/or other flexible structures.

Display cover layer 14CG may be formed from polymer, glass, crystallinematerials such as sapphire, other materials, and/or combinations ofthese materials. To enhance flexibility, a portion of layer 14CG thatoverlaps and extends along bend axis 28 may be locally thinned (e.g.,this portion may be thinned relative to portions of layer 14CG that donot overlap bend axis 28). The thickness of layer 14CG (e.g., thenon-thinned portions of layer 14CG) may be 50-200 microns, 70-150microns, 100-200 microns, 100-600 microns, at least 100 microns, atleast 200 microns, less than 600 microns, less than 400 microns, lessthan 250 microns, less than 150 microns, less than 100 microns, at least50 microns, or other suitable thickness.

In the example of FIG. 3, housing 12 has a portion on rear face R thatforms a rear housing wall and has side portions forming sidewalls 12W.The rear housing wall of housing 12 may form a support layer forcomponents in device 10. Housing 12 may also have one or more interiorsupporting layers (e.g., frame structures such as an optional midplate,etc.). These interior supporting layers and the rear housing wall mayhave first and second portions that are coupled to opposing sides of ahinge that is aligned with bend axis 28 (see, e.g., hinge 30 of FIG. 2)or may be sufficiently flexible to bend around bend axis 28.

Electrical components 32 may be mounted in the interior of device 10(e.g., between display 14 and the rear of housing 12. Components 32 mayinclude circuitry of the type shown in FIG. 1 (e.g., control circuitry20, communications circuitry 22, input-output devices 24, batteries,etc.). Display 14 may be mounted on front face F of device 10. Whendevice 10 is folded about axis 28, display cover layer 14CG, displaypanel 14P, and the other structures of device 10 that overlap bend axis28 may flex and bend to accommodate folding.

The outer and/or inner surfaces of display cover layer 14GC may beprovided with coatings. These coatings may include, for example,antireflection coatings, anti-scratch coatings, anti-smudge coatings,and/or other coating layers. Consider, as an example, thecross-sectional side view of display cover layer 14CG of FIG. 4. Asshown in FIG. 4, display cover layer may have an outer surface(outwardly facing surface) such as surface 40 and an opposing innersurface (inwardly facing surface) such as surface 42. A strip-shapedregion of display cover layer 14CG that overlaps and runs parallel tobend axis 28 may be locally thinned (e.g., a groove or other recess thatruns parallel to bend axis 28 may be formed in layer 14CG to formlocally thinned portion 44 of layer 14CG). Locally thinned portion 44 oflayer 14CG may be thinner than other portions of layer 14CG such asnon-thinned portions 46 (which may be, for example, planar glass layerportions of layer 14CG). The presence of portion 44 in display coverlayer 14CG may facilitate bending of display cover layer 14CG about bendaxis 28.

To help planarize inner surface 42 and thereby facilitate mounting ofdisplay panel 14P against inner surface 42 (e.g., with a layer ofadhesive), the elongated recess (groove) in the inner surface of layer14CG that forms thinned portion 44 may be filled with polymer 50.Polymer 50 may be sufficiently flexible to bend about bend axis 28 whendevice 10 is opened and closed. The refractive index of polymer 50 maybe matched to that of display cover layer 14CG to help minimize lightreflections (e.g., by incorporating inorganic nanoparticles in polymer50). For example, at a wavelength of 500 nm, the refractive index ofpolymer 50 may differ from that of layer 14CG by less than 0.15, lessthan 0.1, or less than 0.05 (as examples).

Coating layers 52 may be formed on outer surface 40. Coating layers 52may include, for example, anti-scratch layers (sometimes referred to ashard coats), protective polymer layers, anti-smudge layers, anti-foglayers, antireflection layers, anti-static layers, adhesion layers,and/or other coatings. In some configurations, each of these functionsmay be implemented using a separate respective coating layer. In otherconfigurations, a single layer may serve multiple functions. In general,coatings such as coatings 52 may be formed on outer surface 40 and/orinner surface 42. In the illustrative configuration of FIG. 4, coatings52 are formed on outer surface 40.

Coatings 52 may be provided in any suitable order. As one example, thelowermost coating of coatings 52 (e.g., a coating layer formed directlyon surface 40 of FIG. 4) may be a hard coat or other anti-scratch layerthat helps prevent scratches that could damage layer 14CG. Anantireflection coating may be formed on top of the anti-scratch layer.The antireflection layer may be a thin-film interference filterantireflection coating containing a stack of thin-film layers such asdielectric sublayers of alternating refractive index. One of thethin-film layers may be a conductive layer such as a transparentsemiconductor layer (e.g., an indium tin oxide layer) that serves as anantistatic layer. An anti-smudge coating or anti-fog coating may beformed on top of the antireflection layer. Anti-smudge coatings (e.g.,hydrophobic polymer coatings) may help reduce fingerprints and otherundesired marks on the surfaces of display 14. An example of ananti-smudge coating is a fluoropolymer coating (e.g., a fluoropolymerformed from evaporated perfluoropolyether) that serves as an oleophobiclayer. Fluoropolymers can be adhered to underlying coating layers usingan intervening adhesion layer.

As shown in FIG. 5, the recess in display cover layer 14CG that formslocally thinned portion 44 may have a tapered cross-sectional shape. Asshown in FIG. 5, for example, the top portion of the recess may becharacterized by a width W1 that is narrower than the width W2 of thelower portion of the recess. This type of arrangement may help avoidabrupt transitions in cover glass thickness and may therefore helpreduce stress concentrations while visually obscuring the presence ofthe recess. To help protect display cover layer 14CG (e.g., to avoidhandling-induced defects), one or more coating layers may be formed oninner surface 42. As shown in FIG. 5, for example, protective coatinglayer 54 (e.g., a polymer layer) may be formed on inner surface 42.Layer 54 may have any suitable thickness (e.g., at least 0.05 microns,at least 0.1 microns, at least 0.4 microns, at least 2 microns, at least5 microns, less than 50 microns, less than 20 microns, less than 7microns, less than 3 microns, or other suitable thickness). If desired,a protective polymer layer such as layer 54 may be formed on outersurface 40 (e.g., one of layers 52 of FIG. 4 may be a protective polymerlayer such as layer 54).

Protective layer 54 may be formed on inner surface 42 by depositingpolymer 50 and layer 54 separately (using the same polymer material forboth polymer 50 and layer 54 or using different polymers for polymer 50and layer 54). As an example, polymer 50 may be deposited in the recessforming thinned portion 44 and cured before depositing and curing aprotective polymer layer over polymer 50 and non-thinned areas of innersurface 42.

In another illustrative arrangement, the protective layer on innersurface 42 may be formed as an integral portion of the polymer fillingthe recess in layer 14CG. As shown in FIG. 6, for example, the samepolymer may be used in filling the recess under thinned portion 44(polymer 50) and in forming the protective coating on surface 42(polymer 50′). Polymer 50 and 50′ in this type of arrangement may bedeposited by coating a liquid polymer material onto inner surface 42followed by application of heat, light (e.g., ultraviolet light), and/orcatalyst to promote polymer curing.

During use of device 10, a computer stylus, fingertip, or other externalobject may press against outer surface 40 of display cover layer 14CG(e.g., to supply touch input to a touch sensor that lies between displaypanel 14P and the opposing inner surface of display cover layer 14CG orto supply touch input to a touch sensor that is formed as part ofdisplay panel 14P). Thinned portion 44 of display cover layer 14CG ispreferably sufficiently flexible to allow display cover layer 14CG to bebent about bend axis 28. At the same time, it may be desirable toprevent the region of surface 40 that overlaps bend axis 28 from beingtoo easily depressed inwardly, as this may create an undesirabledetectable difference in the stiffness of outer surface 40 as anexternal object moves across bend axis 28. To help prevent excessiveinward compression of surface 40 in the area of display cover layer 14CGthat overlaps thinned portion 44, stiffening structures that areseparate from display cover layer 14CG may be incorporated into polymer50 in the recess under thinned portion 44. These stiffening structuresmay be particles or may be elongated members (e.g., elongated strips ofmaterial, rods, etc.). The material that forms the stiffening structuresmay be glass, polymer, ceramic, crystalline material such as sapphire,and/or other rigid material (e.g., one or more materials that are have ahigher modulus of elasticity (and are therefore stiffer) than polymer50. By incorporating structures that are more rigid than polymer 50 intopolymer 50, the stiffness of the thinned portion of layer 14CG (e.g.,resistance to localized inward compression) may be locally enhanced,while continuing to allow display 14 to bend freely about axis 28.

Consider, as an example, the arrangement of FIG. 7. As shown in FIG. 7,stiffening structures such as stiffening particles 60 may beincorporated into polymer 50 within the recess under thinned portion 44of display cover layer 14CG. Particles 60 may be spheres or particles ofother shapes and may be formed from a material such as glass with amodulus of elasticity that is greater than that of polymer 50 (e.g.,particles 60 may be glass beads). This stiffens polymer 50 and helpprevent the portion of surface 40 that lies above thinned portion 44from being too easily depressed (e.g., too easily locally deformedinward) due to pressure on surface 40 from the tip of a stylus or otherexternal object. At the same time, because particles 60 are not directlyconnected to each other by any rigid structures (e.g., because there isa portion of polymer 50 between adjacent particles), particles 60 arefree to move relative to each other while polymer 50 is flexed. As aresult, layer 14CG and polymer 50 may still bend freely about bend axis28.

Particles 60 may be any suitable size. Particles may, as an example,have diameters (e.g., a mean diameter) of at least 0.1 microns, at least0.2 microns, at least 0.3 microns, at least 0.5 microns, at least 1microns, at least 2 microns, at least 5 microns, at least 25 microns,0.2-10 microns, 1-20 microns, 1-50 microns, 0.5-50 microns, less than100 microns, less than 50 microns, less than 25 microns, less than 12microns, less than 6 microns, or less than 2.5 microns (as examples).

To help match the refractive index of polymer 50 to that of displaycover layer 14CG, it may be desirable to include index-matchingparticles 62 in polymer 50 in addition to including optional stiffeningstructures such as stiffening particles 60 or other stiffeningstructures. Index-matching particles 62 may, as example, be formed fromparticles of inorganic dielectric (e.g., silica, metal oxides such aszirconia particles, alumina particles, titanic particles, etc.). Suchindex-matching particles may have nanometer-scale sizes and maysometimes be referred to as index-matching nanoparticles. Index-matchingparticles 62 may, as an example, have subwavelength sizes (e.g.,diameters of about 10 nm, 1-100 nm, at least 2 nm, less than 300 nm,less than 250 nm, less than 200 nm, less than 150 nm, less than 100 nm,less than 50 nm, less than 40 nm, 1-50 nm, 2-40 nm etc.). Theconcentration of index-matching particles 62 may be increased toincrease the effective refractive index of polymer 50 and may bedecreased to decrease the effective refractive index of polymer 50. Inthis way, the refractive index of polymer 50 may be matched to that ofdisplay cover layer 14CG and to that of particles 60 or other stiffeningstructures (e.g., to reduce reflections at the interfaces betweenpolymer 50 and these structures).

The diameter of particles 60 may be uniform or particles 60 may includespheres or other particles of different sizes. If desired, the diameter(e.g., mean diameter) of particles 60 may be constant throughout polymer50. In arrangements in which the size of particles 60 varies, thediameters of particles 60 may vary as a function of position in polymer50. As an example, the diameter (e.g., the mean diameter) of particles60 may decrease or otherwise vary as a function of distance d fromsurface 40. In general, any one or more characteristics of particles 60may vary as a function of distance d. As shown in the graph of FIG. 8,one or more characteristics of particles 60 such as characteristic M mayvary continuously (see, e.g., smoothly and continuously decreasing curve64 of FIG. 8) and/or may vary in a stepwise fashion (see, e.g., stepwisedecreasing curve 66 of FIG. 8). Characteristic M may be any suitableparticle characteristic(s) such as particle diameter, particle material,particle refractive index, particle shape, the concentration ofparticles in polymer 50 (e.g., the number of particles per unit volume),and/or other particle characteristic(s).

In arrangements in which the diameter of particles 60 decreases as afunction of increasing distance through polymer 50 away from surface 42at the top of the recess in cover layer 14CG (and therefore as afunction of increasing distance from outer surface 40), there will belarger particles near the top of the recess (e.g., nearer to outersurface 40) that help to stiffen surface 40 and smaller particles nearthe bottom of the recess (e.g., nearer to the rear of layer 14CG). Thepresence of the smaller particles near the bottom of the recess may helpmake the lower portion of polymer 50 more flexible than the upperportion of polymer 50. Because the bottom portion of polymer 50 tends tostretch more than the upper portion of polymer 50 as display cover layer14CG is bent about bend axis 28 (e.g., when the two halves of display 14are being folded toward themselves), the use of a graded particle size(e.g., a stiffening scheme in which the mean diameter of particles 60decreases as a function of increasing distance d) may help provide adesired amount of surface stiffening to the region of surface 40 thatoverlaps polymer 50 while retaining a desired flexibility in displaycover layer 14CG so that device 10 and display 14 can be folded. Anysuitable technique may be used for forming polymer 50 with embeddedstiffening structures such as particles 60 having a gradient in size.With an illustrative configuration, a mixture of liquid polymer materialcontaining particles 60 of varying sizes is used to cover thinned region44 while display cover layer 14CG is resting with its inner surfacefacing upwards. In this type of configuration, the force of gravity willtend to separate particles by size, after which the polymer material canbe cured.

As described in connection with curve 66 of FIG. 8, characteristic M ofparticles 60 may exhibit stepwise variation as a function of distance d.This type of arrangement is shown in the cross-sectional side view ofdisplay cover layer 14CG of FIG. 9. In the example of FIG. 9, polymer 50has been formed using a first layer of polymer 50-1 containing particles60 of a first diameter followed by a second layer of polymer 50-2 (atgreater distance d from surface 40) containing particles 60 of a seconddiameter that is smaller than the first diameter. In this example,polymer 50 was deposited in two layers (e.g., a first layer that wasdeposited as a liquid and cured and a second layer that was deposited asa liquid on the cured first layer and subsequently cured).Configurations with three or more discrete layers each having adifferent size of particle 60 may also be used.

If desired, elongated members formed from glass or other stiffeningmaterial may be incorporated into polymer 50 in locally thinned region44. As shown in FIG. 10, for example, a series of parallel elongatedmembers such as glass strips 70 or other members that extend parallel tobend axis 28 may serve as stiffening structures. Strips 70 may beincorporated into polymer 50 to help vertically stiffen surface 40 inlocally thinned portion 44 of display cover layer 14CG (e.g., to helpprevent surface 40 from being too easily deformed inwardly when theportion of surface 40 that overlaps thinned portion 44 is contacted by acomputer stylus or other external object that presses inwardly onsurface 40). Although strips 70 provide enhanced vertical rigidity tosurface 40 over portion 44, the presence of strips 70 will not reducethe flexibility of display 14 with respect to bending about bend axis28, because strips 70 are free to move with respect to each other andwith respect to thinned portion 44 of display cover layer 14CG asdisplay 14 is folded.

Polymer 50, which fills the recess of thinned portion 44 of displaycover layer 14CG, may extend laterally to cover regions of inner surface42 on non-thinned portions of display cover layer 14CG (see, e.g.,portion 50′, as described in connection with FIG. 6). If desired, aseparate polymer protective coating may be formed on inner surface 42(see, e.g., coating layer 54 of FIG. 5). As described in connection withlayers 52 of FIG. 4, one or more optional layers may be provided onouter surface 40 such as layer 52 of FIG. 10. There may be any suitablenumber of parallel strips 70 in the recess of thinned portion 44. Thereare three strips 70 in the example of FIG. 10. There may be fewer thanthree strips 70 or more than three strips 70, if desired. Strips 70 maybe formed from glass or other rigid transparent material (clear ceramic,sapphire or other crystalline material, etc.). Configurations in whichstrips 70 are glass strips and lie parallel to surfaces 40 and 42 whendisplay 14 is in an unfolded planar state are sometimes described hereinas an example. The presence of strips 70 helps ensure that surface 40will not be too easily deformed inwardly when contacted by a stylus orother external object. The presence of elongated polymer-filled gapsbetween adjacent strips 70 (e.g., gaps that extend parallel to bend axis28) helps to ensure that display 14 can exhibit sufficient flexibilityto bend about axis 28 when device 10 is folded and unfolded.

In the example of FIG. 11, a display cover layer similar to that of FIG.10 has been constructed using a pair of laminated layers. In locallythinned portion 44, display cover layer 14CG exhibits enhanced localflexibility, because only a single thickness of display cover layermaterial (e.g., a single glass layer) is present (e.g., display coverlayer 14CG-1 is present and display cover layer 14CG-2 is not present inportion 44). In portions 46, display cover layer 14CG includes bothupper display cover layer 14CG-1 and lower display cover layer 14CG-2(e.g., an additional glass layer). Lower display cover layer 14CG-2 isattached to upper display cover layer 14CG-1 by a layer of polymer suchas polymer adhesive 72 (e.g., part of polymer 50 or a separate polymerlayer). Polymer 50 may have portions 50′ that extend to form aprotective inner surface cover layer on surface 42 or a separateprotective polymer layer may be formed on surface 42, as shown in FIG.5. Layer 14CG-2 of FIG. 11 has two halves (e.g., left and right halvesseparated by a gap that forms a recess in display cover layer 14CG underthinned portion 44). The gap in layer 14CG-2 helps enhance theflexibility of layer 14CG so that layer 14CG can bend about bend axis28. Strips 70 and/or other stiffening structures may be embedded inpolymer 50 in the gap formed between the left and right halves of layer14CG.

To help reduce cracks that might weaken strips 70, strips 70 may beetched in a glass etchant (e.g., HF) and/or mechanically polished. Thisprocess and/or other processing techniques may be used to form glassstrips such as strip 70 of FIG. 12, which has a cross-sectional profilewith a rectangular shape having rounded corners 70R. The presence ofrounded corners 70R or other curved surface profiles may help preventchips and other damage in the event that adjacent strips 70 contact eachother and may help to remove cracks that could lead to fracturing.

The thickness of display cover layer 14CG in region 44 may be 30-200microns, at least 10 microns, at least 20 microns, less than 500microns, less than 300 microns, less than 200 microns, less than 100microns, or other suitable thickness that is less than the thickness ofdisplay cover layer 14CG in non-thinned regions. The thickness of glassstrips 70 (which may be the same as the thickness of layer 14CG-2 in theconfiguration of FIG. 11) may be 30-200 microns, at least 10 microns, atleast 20 microns, less than 500 microns, less than 300 microns, lessthan 200 microns, less than 100 microns, or other suitable thickness.The thickness of display cover layer 14CG in regions 46 may be 30-600microns, 100-600 microns, 100-400 microns, at least 30 microns, at least100 microns, at least 200 microns, less than 3000 microns, less than1000 microns, less than 600 microns, less than 400 microns, or othersuitable thickness.

Strips 70 may each have the same width or the widths of strips 70 maydiffer from each other. The width of each of strips 70 may be at least10 microns, at least 100 microns, at least 500 microns, at least 1.5 mm,at least 3 mm, at least 6 mm, 1-10 mm, 1-3 mm, 0.5-2 mm, less than 10mm, less than 7 mm, less than 4 mm, less than 2.5 mm, less than 1.5 mm,or other suitable width. The length of each strip 70 may span the entirewidth of device 10 (e.g., each strip 70 may have a length equal to thedistance that bend axis 28 traverses across device 10 and display 14) oreach of strips 70 may be divided into two or more segments along itslength (e.g., a strip may have two halves or more segments arrangedend-to-end that collectively span the width of display 14). Strips 70may be formed from the same material (e.g., the same glass) as displaycover layer 14CG or may be formed from a material with an identical orsimilar refractive index. This may help match the refractive indexvalues of strips 70 to the refractive index of display cover layer 14CG(e.g., so that index of strips 70 differs from the index of layer 14CGand from the index of polymer 50 by less than 0.15, by less than 0.1, orby less than 0.05, as examples).

To help enhance the rigidity of surface 40 over thinned portion 44,polymer 50 of FIGS. 10 and 11 may include glass beads or otherstiffening particles in addition to stiffening structures such as strips70 (e.g., the polymer-filled groove under portion 44 may contain bothstiffening structures such as glass beads and stiffening structures suchas glass strips). The stiffening particles may be particles such asparticles 60 of FIG. 7. Such particles may have a single diameter or mayhave varying diameters (e.g., diameters that vary as shown by curves 64and 66 of FIG. 8 or that otherwise decrease as a function of increasingdistance into polymer 50 away from outer surface 40). If desired,index-matching nanoparticles 62 may also be incorporated into polymer 50to help match the refractive index of polymer 50 to that of strips 70and display cover layer 14CG (e.g., thinned portion 44).

Polymer 50 may be stiffened and/or index-matched to display cover layer14CG using an inhomogeneous mixture of embedded particles (particles ofdifferent sizes, shapes, and/or materials) or a homogenous mixture ofembedded particles. Embedded particles (e.g., particles 60 and/or 62and/or other particles in polymer 50) may be formed from materialshaving a refractive index that differs from that of polymer 50 (e.g.,particles for index matching polymer 50 to cover layer 14CG andoptionally stiffening polymer 50) and/or from materials having a matchedrefractive index (e.g., particles used for stiffening polymer 50 but notused to change the refractive index of polymer 50). The embeddedparticles may be nanoparticles and/or larger particles having fixedcharacteristics throughout polymer 50 and/or having one or morecharacteristics that vary as a function of distance through thethickness of polymer 50.

The embedded particles may, for example, have a mean size or otherattribute (e.g., composition, shape, etc.) that varies as a function ofposition within polymer 50 (e.g., as a function of distance d) in asmooth and continuous (non-stepwise) fashion and/or in a stepwisefashion). Embedded particles may be formed from glass beads, other glassparticles, and/or other dielectric (e.g., beads or other particlesformed from silica, metal oxides such as zirconia particles, aluminaparticles, titania particles, etc.). The embedded particles may bespherical, plate-shaped (e.g., flakes), rod-shaped, and/or may haveother suitable shapes.

In an illustrative configuration, the embedded particles are particlescharacterized by a mean diameter. The mean diameter of the particles maybe 0.01 microns to 50 microns, 0.05 microns to 25 microns, 0.01 micronsto 25 microns, 0.03 microns to 50 microns, at least 0.01 microns, atleast 0.1 microns, at least 1 micron, less than 50 microns, less than 5microns, less than 0.5 microns, etc. The mean diameter may be fixedthroughout a homogenous mixture in polymer 50 and/or may have a valuewithin these ranges or other suitable ranges that varies as a functionof position within polymer 50 (e.g., as a function of distance d), etc.As an example, embedded dielectric particles in polymer 50 may becharacterized by a mean diameter of 0.01 microns to 50 microns (or othersuitable range) that is fixed through polymer 50 or that varies as afunction of distance (e.g., distance d) through polymer 50 while servingto enhance resistance of the outer surface of display cover layer 14CGover the locally thinned portion of the display cover layer to inwarddeformation and while allowing the display cover layer to bend aboutbend axis 28.

As described above, one aspect of the present technology is thegathering and use of information such as information from input-outputdevices. The present disclosure contemplates that in some instances,data may be gathered that includes personal information data thatuniquely identifies or can be used to contact or locate a specificperson. Such personal information data can include demographic data,location-based data, telephone numbers, email addresses, twitter ID's,home addresses, data or records relating to a user's health or level offitness (e.g., vital signs measurements, medication information,exercise information), date of birth, username, password, biometricinformation, or any other identifying or personal information.

The present disclosure recognizes that the use of such personalinformation, in the present technology, can be used to the benefit ofusers. For example, the personal information data can be used to delivertargeted content that is of greater interest to the user. Accordingly,use of such personal information data enables users to calculatedcontrol of the delivered content. Further, other uses for personalinformation data that benefit the user are also contemplated by thepresent disclosure. For instance, health and fitness data may be used toprovide insights into a user's general wellness, or may be used aspositive feedback to individuals using technology to pursue wellnessgoals.

The present disclosure contemplates that the entities responsible forthe collection, analysis, disclosure, transfer, storage, or other use ofsuch personal information data will comply with well-established privacypolicies and/or privacy practices. In particular, such entities shouldimplement and consistently use privacy policies and practices that aregenerally recognized as meeting or exceeding industry or governmentalrequirements for maintaining personal information data private andsecure. Such policies should be easily accessible by users, and shouldbe updated as the collection and/or use of data changes. Personalinformation from users should be collected for legitimate and reasonableuses of the entity and not shared or sold outside of those legitimateuses. Further, such collection/sharing should occur after receiving theinformed consent of the users. Additionally, such entities shouldconsider taking any needed steps for safeguarding and securing access tosuch personal information data and ensuring that others with access tothe personal information data adhere to their privacy policies andprocedures. Further, such entities can subject themselves to evaluationby third parties to certify their adherence to widely accepted privacypolicies and practices. In addition, policies and practices should beadapted for the particular types of personal information data beingcollected and/or accessed and adapted to applicable laws and standards,including jurisdiction-specific considerations. For instance, in theUnited States, collection of or access to certain health data may begoverned by federal and/or state laws, such as the Health InsurancePortability and Accountability Act (HIPAA), whereas health data in othercountries may be subject to other regulations and policies and should behandled accordingly. Hence different privacy practices should bemaintained for different personal data types in each country.

Despite the foregoing, the present disclosure also contemplatesembodiments in which users selectively block the use of, or access to,personal information data. That is, the present disclosure contemplatesthat hardware and/or software elements can be provided to prevent orblock access to such personal information data. For example, the presenttechnology can be configured to allow users to select to “opt in” or“opt out” of participation in the collection of personal informationdata during registration for services or anytime thereafter. In anotherexample, users can select not to provide certain types of user data. Inyet another example, users can select to limit the length of timeuser-specific data is maintained. In addition to providing “opt in” and“opt out” options, the present disclosure contemplates providingnotifications relating to the access or use of personal information. Forinstance, a user may be notified upon downloading an application (“app”)that their personal information data will be accessed and then remindedagain just before personal information data is accessed by the app.

Moreover, it is the intent of the present disclosure that personalinformation data should be managed and handled in a way to minimizerisks of unintentional or unauthorized access or use. Risk can beminimized by limiting the collection of data and deleting data once itis no longer needed. In addition, and when applicable, including incertain health related applications, data de-identification can be usedto protect a user's privacy. De-identification may be facilitated, whenappropriate, by removing specific identifiers (e.g., date of birth,etc.), controlling the amount or specificity of data stored (e.g.,collecting location data at a city level rather than at an addresslevel), controlling how data is stored (e.g., aggregating data acrossusers), and/or other methods.

Therefore, although the present disclosure broadly covers use ofinformation that may include personal information data to implement oneor more various disclosed embodiments, the present disclosure alsocontemplates that the various embodiments can also be implementedwithout the need for accessing personal information data. That is, thevarious embodiments of the present technology are not renderedinoperable due to the lack of all or a portion of such personalinformation data.

The foregoing is merely illustrative and various modifications can bemade to the described embodiments. The foregoing embodiments may beimplemented individually or in any combination.

What is claimed is:
 1. An electronic device, comprising: a foldablehousing that is configured to bend about a bend axis; a flexible displaypanel that overlaps the bend axis; and a display cover layer thatoverlaps the flexible display panel, wherein the display cover layer hasan inner surface that faces the flexible display panel and has anopposing outer surface and wherein the display cover layer has a grooveextending along the bend axis that forms a locally thinned portion ofthe display cover layer; polymer in the groove; and stiffeningstructures embedded in the polymer that enhance resistance of the outersurface over the locally thinned portion to inward deformation whileallowing the display cover layer to bend about the bend axis.
 2. Theelectronic device defined in claim 1 wherein the stiffening structurescomprise particles.
 3. The electronic device defined in claim 2 whereinthe particles have a mean diameter that varies as a function of distancethrough the polymer.
 4. The electronic device defined in claim 3 whereinthe particles have a first mean diameter at a first distance into thepolymer from the outer surface and wherein the particles have a secondmean diameter that is smaller than the first diameter at a seconddistance into the polymer from the outer surface that is larger than thefirst distance.
 5. The electronic device defined in claim 4 wherein themean diameter of the particles varies smoothly and continuously as afunction of distance through the polymer.
 6. The electronic devicedefined in claim 4 wherein the mean diameter of the particles ischaracterized by a stepwise change as a function of distance through thepolymer.
 7. The electronic device defined in claim 3 wherein the meandiameter is 0.5 microns to 50 microns.
 8. The electronic device definedin claim 7 wherein the particles comprise glass particles.
 9. Theelectronic device defined in claim 2 wherein the particles compriseglass beads.
 10. The electronic device defined in claim 9 wherein theglass beads have diameters of 1-50 microns and wherein the polymercontains inorganic nanoparticles of less than 250 nm in diameter. 11.The electronic device defined in claim 1 wherein the stiffeningstructures comprise glass strips.
 12. The electronic device defined inclaim 11 wherein the glass strips have rectangular cross-sectionalprofiles with rounded corners.
 13. The electronic device defined inclaim 1 wherein the stiffening structures comprise glass strips andglass beads.
 14. The electronic device defined in claim 13 wherein thepolymer contains nanoparticles with diameters of less than 300 nm at aconcentration, wherein the polymer has a first refractive index, whereinthe display cover layer has a second refractive index, and whereinconcentration is configured to ensure that the first refractive indexand the second refractive index differ by less than 0.05.
 15. Theelectronic device defined in claim 1 wherein the display cover layercomprise a glass layer and has a non-thinned portion, the electronicdevice further comprising a polymer coating on the inner surface of thenon-thinned portion.
 16. The electronic device defined in claim 15wherein the polymer coating is an extended portion of the polymer in thegroove.
 17. The electronic device defined in claim 15 wherein thepolymer coating and the polymer in the groove are different polymermaterials.
 18. An electronic device, comprising: a foldable housing thatis configured to bend about a bend axis; a flexible display panel thatoverlaps the bend axis; and a glass display cover layer that overlapsthe flexible display panel, wherein the glass display cover layer has anouter surface and has an inner surface facing the flexible display paneland wherein the glass display cover layer has a recess in the innersurface that extends along the bend axis and forms a locally thinnedportion of the glass display cover layer; and polymer in the recess thatcontains glass strips that stiffen the outer surface over the recesswhile allowing the glass display cover layer to bend about the bendaxis.
 19. The electronic device defined in claim 18 further comprisingglass beads in the polymer.
 20. A foldable display, comprising: afoldable display panel configured to fold about a bend axis; and adisplay cover layer that overlaps the foldable display panel, whereinthe display cover layer has a recess forming a locally thinned portionof the display cover layer that extends along the bend axis, the displaycover layer comprising: a first layer of glass that overlap the flexibledisplay panel; a second layer of glass attached to an inner surface ofthe first layer of glass by a polymer layer, wherein the second layer ofglass has first and second halves separated by a gap that forms therecess; and polymer containing glass stiffening structures in therecess.
 21. The foldable display defined in claim 20 wherein the glassstiffening structures comprise glass beads.
 22. The foldable displaydefined in claim 20 wherein at least one characteristic of the glassbeads varies as a function of distance through the polymer layer. 23.The foldable display defined in claim 20 wherein the glass stiffeningstructures comprise glass strips that extend parallel to the bend axis.24. The foldable display defined in claim 23 wherein the glassstiffening structures further comprise glass beads, the foldable displayfurther comprising: nanoparticles in the polymer having diameters lessthan 200 nm; a polymer coating on a surface of the second glass layerfacing the flexible display panel; and an antireflection coating on anouter surface of the first layer of glass facing away from the flexibledisplay panel.
 25. An electronic device, comprising: a foldable housingthat is configured to bend about a bend axis; a flexible display panelthat overlaps the bend axis; and a display cover layer that overlaps theflexible display panel, wherein the display cover layer has an innersurface that faces the flexible display panel and has an opposing outersurface and wherein the display cover layer has a groove extending alongthe bend axis that forms a locally thinned portion of the display coverlayer; polymer in the groove; and dielectric particles embedded in thepolymer that enhance resistance of the outer surface over the locallythinned portion to inward deformation while allowing the display coverlayer to bend about the bend axis, wherein the dielectric particles havea mean diameter between 0.01 microns and 50 microns and wherein the meandiameter varies as a function of distance through the polymer.